The dust has scarcely settled after the rumpus over the treatment of torture in Zero Dark Thirty and here was Complicit (C4) prodding the same hornets’ nest.

Writer Guy Hibbert gave us a story centred on terrorism that wasn’t so much a thriller but a moral maze, one that had me questioning my own ethical satnav long after the credits rolled.

Told through the eyes of MI5 agent Edward Ekubo, played with steely understatement by David Oyelowo, Complicit posed some tough questions, the most nagging one being: ‘Do the ends justify the means?’ Ekubo was convinced that Waleed Ahmed, the British Muslim he’d been tracking, was on the verge of making his move and facilitating a ricin attack in Britain.

But with official channels dithering and zero hour approaching, Ekubo’s only option – at least the way he saw it – was to let the ruthless Colonel Hazem Ashraf loose on Ahmed.

Around this central, thorny, question, which played havoc with your sympathies, Hibbert stealthily built up a picture of shadowy intelligence services mired in weary bureaucracy, a system built on prejudice and privilege – and one where truth came quite a long way down the list of priorities. There was a hint of the opening of Homeland about the mystery at Complicit’s core: was Ekubo the hero or the villain of the piece, a moral crusader or a dangerous obsessive?

Admittedly, it took a while to fall under Complicit’s spell. At first, it was hard to be drawn into this sterile world, the story seemed abstract and impenetrable. But once Ekubo was dispatched to Egypt, where he encountered his foe, patience was paid back big time.

The verbal sparring between Oyelowo and Arsher Ali as Ahmed was an electric battle between opposing wills and worlds, each deeply entrenched in conviction. Ahmed toyed with his inquisitor, hisline: ‘It might be all in your imagination. That’s what terror is,’ striking a chill into the soul.

There was a twist and maybe it was a little too clever for its own good. Ekubo discovered the cost of sidestepping official policy and not playing by the rules of a club of which he’d never been a member. He’d been fighting for the greater good but was left on his own, hung out to dry. As morals go, it was a bitter one to swallow.